Radio communication device and response signal diffusion method

ABSTRACT

Provided is a radio communication device which can suppress inter-code interference between an ACK/NACK signal and a CQI signal which are code-multiplexed. A diffusion unit ( 214 ) diffuses the ACK/NACK signal inputted from a judgment unit ( 208 ) by using a ZC sequence. A diffusion unit ( 219 ) diffuses the CQI signal by using a cyclic shift ZC sequence. By using a Walsh sequence, a diffusion unit ( 216 ) further diffuses the ACK/NACK signal which has been diffused by using the ZC sequence. A control unit ( 209 ) controls the diffusion unit ( 214 ), the diffusion unit ( 216 ), and the diffusion unit ( 219 ) so that the minimum value of the difference between the CQI signals from a plurality of mobile stations and a cyclic shift amount of the ACK/NACK signal is not smaller than the minimum value of the difference between the cyclic shift amounts of the ACK/NACK signals from the plurality of mobile stations.

BACKGROUND

1. Technical Field

The present disclosure relates to a radio communication apparatus andresponse signal spreading method.

2. Background Art

In mobile communications, ARQ (Automatic Repeat Request) is applied todownlink data from a radio communication base station apparatus(hereinafter abbreviated to “base station”) to a radio communicationmobile station apparatus (hereinafter abbreviated to “mobile station”).That is to say, a mobile station feeds back a response signalrepresenting error detection results of downlink data, to the basestation. A mobile station performs a CRC (Cyclic Redundancy Check) ondownlink data, and, if CRC=OK is found (no error), feed back an ACK(ACKnowledgement), and, if CRC=NG is found (error present), feed back aNACK (Negative ACKnowledgement), as a response signal to the basestation. This response signal is transmitted to the base station usingan uplink control channel such as a PUCCH (Physical Uplink ControlChannel), for example.

Furthermore, a base station transmits control information for reportinga downlink data resource allocation result to a mobile station. Thiscontrol information is transmitted to a mobile station using a downlinkcontrol channel such as an L1/L2CCH (L1/L2 Control Channel), forexample. Each L1/L2CCH occupies one or a plurality of CCEs (ControlChannel Elements). When one L1/L2CCH occupies a plurality of CCEs, oneL1/L2CCH occupies a consecutive plurality of CCEs. The base stationallocates an L1/L2CCH from among a plurality of L1/L2CCHs for eachmobile station in accordance with the number of CCEs necessary forcarrying control information, and transmits control information mappedon a physical resource corresponding to a CCE occupied by each L1/L2CCH.

In order to use downlink communication resources efficiently, mutuallymapping between CCE's and PUCCH's has been investigated. Each mobilestation can determine a PUCCH to be used for transmission of a responsesignal from that mobile station from a CCE corresponding to a physicalresource to which control information for that mobile station is mappedin accordance with this mapping.

Also, investigation has been carried out into code-multiplexing aplurality of response signals from a plurality of mobile stations bymeans of spreading using a ZC (Zadoff-Chu) sequence and Walsh sequence,as shown in FIG. 1 (see Non-Patent Document 1). In FIG. 1, (W₀, W₁, W₂,W₃) represents a Walsh sequence with a sequence length of four. As shownin FIG. 1, in a mobile station, first, a response signal of ACK or NACKis subject to first spreading to one symbol by a ZC sequence (with asequence length of twelve) in the frequency domain. Then a responsesignal subjected to first spreading is subject to an IFFT (Inverse FastFourier Transform) in association with W₀ to W₃. A response signal thathas been spread in the frequency domain by a ZC sequence with a sequencelength of twelve is transformed to a time-domain ZC sequence with asequence length of twelve by this IFFT. Then this signal subjected tothe IFFT is subject to second spreading using a Walsh sequence (with asequence length of four). That is to say, one response signal isarranged in four symbols S₀ through S₃. Response signal spreading isalso performed in a similar way in other mobile stations using a ZCsequence and Walsh sequence. However, different mobile stations use ZCsequences with mutually different Cyclic Shift values in the timedomain, or mutually different Walsh sequences. Here, since thetime-domain sequence length of a ZC sequence is twelve, it is possibleto use twelve ZC sequences with cyclic shift values of 0 through 11generated from the same ZC sequence. Also, since the sequence length ofa Walsh sequence is four, four mutually different Walsh sequences can beused. Therefore, in an ideal communication environment, response signalsfrom a maximum of forty eight (12×4) mobile stations can becode-multiplexed.

Here, cross-correlation between ZC sequences with mutually differentcyclic shift values generated from the same ZC sequence is 0. Therefore,in an ideal communication environment, as shown in FIG. 2, a pluralityof code-multiplexed response signals spread by ZC sequences withmutually different cyclic shift values (cyclic shift values of 0 through11) can be separated without inter-code interference in the time domainby correlation processing in the base station.

In the case of the 3GPP LTE (3rd Generation Partnership Project LongTerm Evolution) PUCCH, a CQI (Channel Quality Indicator) signal iscode-multiplexed as well as the above-described ACK/NACK signals. Whilean ACK/NACK signal is 1-symbol information, as shown in FIG. 1, a CQIsignal is 5-symbol information. As shown in FIG. 3, a mobile stationspreads a CQI signal by a ZC sequence with a sequence length of twelveand cyclic shift value P, and transmits the spread CQI signal afterperforming IFFT processing. Since a Walsh sequence is not applied to aCQI signal, a Walsh sequence cannot be used in the base station forseparation of an ACK/NACK signal and CQI signal. Thus, by performingdespreading by a ZC sequence of an ACK/NACK signal and CQI signal spreadby ZC sequences corresponding to different cyclic shifts, a base stationcan separate the ACK/NACK signal and CQI signal with almost nointer-code interference.

However, due to an influence of transmission timing difference in mobilestation, multipath delayed waves, frequency offset, and so forth, aplurality of ACK/NACK signals and CQI signals from a plurality of mobilestations do not necessarily reach a base station at the same time. Totake the case of an ACK/NACK signal as an example, as shown in FIG. 4,if the transmission timing of an ACK/NACK signal spread by a ZC sequencewith a cyclic shift value of 0 is delayed from the correct transmissiontiming, the correlation peak of the ZC sequence with a cyclic shiftvalue of 0 appears in the detection window of a ZC sequence with acyclic shift value of 1. Also, as shown in FIG. 5, if there is a delayedwave in an ACK/NACK spread by a ZC sequence with a cyclic shift value of0, interference leakage due to that delayed wave appears in thedetection window of a ZC sequence with a cyclic shift value of 1. Thatis to say, in these cases, a ZC sequence with a cyclic shift value of 1receives interference from a ZC sequence with a cyclic shift value of 0.Therefore, in these cases, separability of an ACK/NACK signal spread bya ZC sequence with a cyclic shift value of 0 and an ACK/NACK signalspread by a ZC sequence with a cyclic shift value of 1 degrades. That isto say, if ZC sequences with mutually adjacent cyclic shift values areused, there is a possibility of ACK/NACK signal separability degrading.

Thus, heretofore, when performing code multiplexing of a plurality ofresponse signals by ZC sequence spreading, a cyclic shift valuedifference (cyclic shift interval) has been provided between ZCsequences that is sufficient to prevent the occurrence of inter-codeinterference between ZC sequences. For example, the cyclic shift valuedifference between ZC sequences is made 2, and of twelve ZC sequenceswith cyclic shift values of 0 through 11, only the six ZC sequencescorresponding to cyclic shift values 0, 2, 4, 6, 8, and 10 are used forfirst spreading of a response signal. Therefore, when using a Walshsequence with a sequence length of four for second spreading of aresponse signal, response signals from a maximum of twenty four (6×4)mobile stations can be code-multiplexed.

In Non-Patent Document 2, an example is disclosed in which, on aresponse signal from a mobile station, first spreading is performedusing six ZC sequences with cyclic shift values 0, 2, 4, 6, 8, and 10,and second spreading is performed using Walsh sequences with sequencelength of four. FIG. 6 is a drawing showing, by a mesh structure, anarrangement of CCEs that can be allocated to mobile stations forACK/NACK signal transmission use (hereinafter abbreviated to “ACK/NACKuse”). Here, it is assumed that a CCE number and a PUCCH number definedby a ZC sequence cyclic shift value and Walsh sequence number are mappedon a one-to-one basis. That is to say, it is assumed that CCE #1 andPUCCH #1, CCE #2 and PUCCH #2, CCE #3 and PUCCH #3, and so on, aremutually mapped (the same applying subsequently). In FIG. 6, thehorizontal axis indicates a ZC sequence cyclic shift value, and thevertical axis indicates a Walsh sequence number. Since inter-codeinterference is extremely unlikely to occur between Walsh sequences #0and #2, as shown in FIG. 6 ZC sequences with the same cyclic shiftvalues are used for CCEs subjected to second spreading by Walsh sequence#0 and CCEs subjected to second spreading by Walsh sequence #2.

-   Non-patent Document 1: Multiplexing capability of CQIs and ACK/NACKs    from different UEs    (ftp://ftp.3gpp.org/TSG_RAN/WG1_RL1/TSGR1_(—)49/Docs/R1-072315.zip)-   Non-patent Document 2: Signaling of Implicit ACK/NACK resources    (ftp://ftp.3 gpp.org/TSG_RAN/WG1_RL1/TSGR1_(—)49/Docs/R1-073006.zip)

BRIEF SUMMARY

As described above, in the case of the 3GPP LTE PUCCH, a CQI signal iscode-multiplexed as well as an ACK/NACK signal. Therefore, it isconceivable for provision to be made so that, of the CCEs having the2-cyclic-shift-interval mesh structure shown in FIG. 6, CCEs using ZCsequences with a cyclic shift value of three and a cyclic shift value of4 are employed for CQI use, and are not employed for ACK/NACK use. Suchan arrangement of CCEs that can be allocated for CQI use and forACK/NACK use is shown in FIG. 7. A problem with the mesh structure shownin FIG. 7 is that the cyclic shift interval between CCE #3 or CCE #15and CCE #9 becomes 1, and inter-code interference between ZC sequencesincreases.

An embodiment provides a radio communication apparatus and responsesignal spreading method that facilitates suppressing inter-codeinterference between an ACK/NACK signal and CQI signal that arecode-multiplexed.

An embodiment of a radio communication apparatus employs a configurationhaving: a first spreading section that performs first spreading of afirst response signal or second response signal using one of a pluralityof first sequences that are mutually separable because of mutuallydifferent cyclic shift values; a second spreading section that performssecond spreading of the first response signal after first spreadingusing one of a plurality of second sequences; and a control section thatcontrols the first spreading section and the second spreading section sothat a minimum value of a difference in cyclic shift values between thefirst response signal and the second response signal from a plurality ofmobile stations is greater than or equal to a minimum value of adifference in cyclic shift values between the second response signalsfrom the plurality of mobile stations.

An embodiment facilitates suppressing inter-code interference between anACK/NACK signal and a CQI signal that are code-multiplexed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a drawing showing a response signal spreading method(conventional);

FIG. 2 is a drawing showing correlation processing of response signalsspread by a ZC sequence (in the case of an ideal communicationenvironment);

FIG. 3 is a drawing showing a CQI signal spreading method(conventional);

FIG. 4 is a drawing showing correlation processing of response signalsspread by a ZC sequence (when there is transmission timing difference);

FIG. 5 is a drawing showing correlation processing of response signalsspread by a ZC sequence (when there is a delayed wave);

FIG. 6 is a drawing showing mapping between a ZC sequence, Walshsequence, and CCEs (conventional case 1);

FIG. 7 is a drawing showing mapping between a ZC sequence, Walshsequence, and CCEs (conventional case 1);

FIG. 8 is a drawing showing the configuration of a base stationaccording to an embodiment;

FIG. 9 is a drawing showing the configuration of a mobile stationaccording to an embodiment;

FIG. 10 is a drawing showing CCEs corresponding to PUCCHs used by mobilestations according to an embodiment 1;

FIG. 11 is a drawing showing a variation of CCEs corresponding to PUCCHsused by mobile stations according to an embodiment;

FIG. 12 is a drawing showing CCEs corresponding to PUCCHs used by mobilestations according to an embodiment;

FIG. 13 is a drawing showing a variation of CCEs corresponding to PUCCHsused by mobile stations according to an embodiment;

FIG. 14 is a drawing showing CCEs corresponding to PUCCHs used by mobilestations according to an embodiment 3;

FIG. 15 is a drawing for explaining CCEs corresponding to PUCCHs used bymobile stations according to an embodiment;

FIG. 16 is a drawing for explaining CCEs corresponding to PUCCHs used bymobile stations according to an embodiment; and

FIG. 17 is a drawing showing a variation of CCEs corresponding to PUCCHsused by mobile stations according to an embodiment.

DETAILED DESCRIPTION

Now, example embodiments will be described in detail with reference tothe accompanying drawings.

Embodiment 1

The configuration of base station 100 according to Embodiment 1 is shownin FIG. 8, and the configuration of mobile station 200 according toEmbodiment 1 is shown in FIG. 9.

To prevent the description from becoming complex, FIG. 8 showscomponents relating to the transmission of downlink data and uplinkreception of an ACK/NACK signal corresponding to that downlink data,closely related to the present disclosure, while components relating tothe reception of uplink data are omitted from the drawing and thedescription. Similarly, FIG. 9 shows components relating to thereception of downlink data, and uplink transmission of an ACK/NACKsignal corresponding to that downlink data, closely related to thepresent disclosure, while components relating to the transmission ofuplink data are omitted from the drawing and the description.

In the following description, a case is described in which a ZC sequenceis used for first spreading and a Walsh sequence is used for secondspreading. However, as well as ZC sequences, sequences that are mutuallyseparable because of mutually different cyclic shift values may also beused for first spreading, and similarly, an orthogonal sequence otherthan a Walsh sequence may be used for second spreading.

In the following description, a case is described in which a ZC sequencewith a sequence length of twelve and a Walsh sequence with a sequencelength of three (W₀, W₁, W₂) are used. However, the present disclosureis not limited to these sequence lengths.

In the following description, twelve ZC sequences with cyclic shiftvalues of 0 through 11 are denoted by ZC #0 through ZC #11, and threeWalsh sequences with sequence numbers 0 through 2 are denoted by W #0through W #2.

In the following description, it is assumed that L1/L2CCH #1 occupiesCCE #1, L1/L2CCH #2 occupies CCE #2, L1/L2CCH #3 occupies CCE #3,L1/L2CCH #4 occupies CCE #4 and CCE #5, L1/L2CCH occupies CCE #6 and CCE#7, L1/L2CCH #6 occupies CCE #8 through CCE #11, and so on.

In the following description, it is assumed that a CCE number and aPUCCH number defined by a ZC sequence cyclic shift value and Walshsequence number are mapped on a one-to-one basis. That is to say, it isassumed that CCE #1 and PUCCH #1, CCE #2 and PUCCH #2, CCE #3 and PUCCH#3 and so on, are mutually mapped.

As explained above, in order to use downlink communication resourcesefficiently in mobile communication, a mobile station determines a PUCCHto be used for transmission of a response signal from that mobilestation from a CCE corresponding to a physical resource to whichL1/L2CCH control information for that mobile station is mapped.Therefore, base station 100 according to this embodiment allocates toeach mobile station an L1/L2CCH comprising a CCE that is appropriate asa PUCCH for that mobile station.

In base station 100 shown in FIG. 8, control information generationsection 101 generates control information for carrying a resourceallocation result per mobile station, and outputs this controlinformation to control channel allocation section 102 and encodingsection 103. Control information, provided per mobile station, includesmobile station ID information indicating the mobile station to which thecontrol information is addressed. For example, CRC that is masked by anID number of a control information report destination mobile station isincluded in control information as mobile station ID information.Control information of each mobile station is encoded by encodingsection 103, modulated by modulation section 104, and inputted tomapping section 108.

Control channel allocation section 102 allocates an L1/L2CCH from amonga plurality of L1/L2CCHs for each mobile station in accordance with thenumber of CCEs necessary for carrying control information. Here, controlchannel allocation section 102 references a CCE corresponding to a PUCCHof each mobile station and allocates an L1/L2CCH to each mobile station.Details of CCEs corresponding to PUCCHs of mobile stations will be givenlater herein. Control channel allocation section 102 outputs a CCEnumber corresponding to an allocated L1/L2CCH to mapping section 108.For example, when the number of CCEs necessary for carrying controlinformation to mobile station #1 is 1 and L1/L2CCH #1 has consequentlybeen allocated to mobile station #1, control information generationsection 101 outputs CCE number #1 to mapping section 108. And when thenumber of CCEs necessary for carrying control information to mobilestation #1 is four and L1/L2CCH #6 has consequently been allocated tomobile station #1, control information generation section 101 outputsCCE numbers #8 through #11 to mapping section 108.

On the other hand, encoding section 105 encodes transmission data(downlink data) to each mobile station, and outputs this data toretransmission control section 106.

At the time of an initial transmission, retransmission control section106 holds encoded transmission data of each mobile station, and alsooutputs this data to modulation section 107. Retransmission controlsection 106 holds transmission data until an ACK from a mobile stationis received as input from determination section 118. If a NACK from amobile station is received as input from determination section 118—thatis, at the time of a retransmission—retransmission control section 106outputs transmission data corresponding to that NACK to modulationsection 107.

Modulation section 107 modulates encoded transmission data received asinput from retransmission control section 106, and outputs this data tomapping section 108.

At the time of control information transmission, mapping section 108maps control information received as input from modulation section 104on a physical resource in accordance with a CCE number received as inputfrom control channel allocation section 102, and outputs this to IFFTsection 109. That is to say, mapping section 108 maps controlinformation of each mobile station on a subcarrier corresponding to aCCE number in a plurality of subcarriers comprised of an OFDM symbol.

On the other hand, at the time of downlink data transmission, mappingsection 108 maps transmission data for each mobile station on a physicalresource in accordance with a resource allocation result, and outputsthis data to IFFT section 109. That is to say, mapping section 108 mapstransmission data of each mobile station on one of a plurality ofsubcarriers comprised of an OFDM symbol in accordance with a resourceallocation result.

IFFT section 109 performs IFFT processing on a plurality of subcarriersto which control information or transmission data is mapped to generatean OFDM symbol, and outputs this to CP (Cyclic Prefix) adding section110.

CP adding section 110 adds the same signal as at the end of the OFDMsymbol to the front of the OFDM symbol as a CP.

Radio transmission section 111 performs transmission processing such asD/A conversion, amplification, and up-conversion on an OFDM symbol witha CP, and transmits the symbol to mobile station 200 (FIG. 9) fromantenna 112.

Meanwhile, radio reception section 113 receives a signal transmittedfrom mobile station 200 via antenna 112, and performs receptionprocessing such as down-conversion and A/D conversion on the receivedsignal. In the received signal, an ACK/NACK signal transmitted from aparticular mobile station is code-multiplexed with a CQI signaltransmitted from another mobile station.

CP removal section 114 removes a CP added to the signal after receptionprocessing.

Correlation processing section 115 finds a correlation value between thesignal received as input from CP removal section 114 and a ZC sequenceused for first spreading in mobile station 200. That is to say,correlation processing section 115 outputs a correlation result found byusing a ZC sequence corresponding to a cyclic shift value allocated toan ACK/NACK signal, and a correlation result found by using a ZCsequence corresponding to a cyclic shift value allocated to a CQIsignal, to separation section 116.

Based on correlation values received as input from correlationprocessing section 115, separation section 116 outputs an ACK/NACKsignal to despreading section 117, and outputs a CQI signal todemodulation section 119.

Despreading section 117 performs despreading of an ACK/NACK signalreceived as input from separation section 116 by a Walsh sequence usedfor second spreading in mobile station 200, and outputs a signal afterdespreading to determination section 118.

Determination section 118 detects a ACK/NACK signal of each mobilestation by detecting a correlation peak on an individual mobile stationbasis using a detection window set for each mobile station in the timedomain. For example, when a correlation peak is detected in detectionwindow #1 for mobile station #1 use, determination section 118 detectsan ACK/NACK signal from mobile station #1, and when a correlation peakis detected in detection window #2 for mobile station #2 use,determination section 118 detects an ACK/NACK signal from mobile station#2. Then determination section 118 determines whether the detectedACK/NACK signal is ACK or NACK, and outputs a ACK or NACK of each mobilestation to retransmission control section 106.

Demodulation section 119 demodulates a CQI signal received as input fromseparation section 116, and decoding section 120 decodes the demodulatedCQI signal and outputs a CQI signal.

Meanwhile, in mobile station 200 shown in FIG. 9, radio receptionsection 202 receives an OFDM symbol transmitted from base station 100via antenna 201, and performs reception processing such asdown-conversion and A/D conversion on the OFDM symbol.

CP removal section 203 removes a CP added to the signal after receptionprocessing.

FFT (Fast Fourier Transform) section 204 performs FFT processing on theOFDM symbol to obtain control information or downlink data mapped on aplurality of subcarriers, and outputs these to extraction section 205.

When control information is received, extraction section 205 extractscontrol information from the plurality of subcarriers and outputs thiscontrol information to demodulation section 206. This controlinformation is demodulated by demodulation section 206, decoded bydecoding section 207, and inputted to determination section 208.

On the other hand, when downlink data is received, extraction section205 extracts downlink data addressed to that mobile station from theplurality of subcarriers and outputs this data to demodulation section210. This downlink data is demodulated by demodulation section 210,decoded by decoding section 211, and inputted to CRC section 212.

CRC section 212 performs error detection using a CRC on downlink dataafter decoding, generates ACK if CRC=OK (no error), or NACK if CRC=NG(error present), and outputs the generated ACK/NACK signal to modulationsection 213. If CRC=OK (no error), CRC section 212 also outputs downlinkdata after decoding as received data.

Determination section 208 determines whether or not control informationreceived as input from decoding section 207 is control informationaddressed to that mobile station. For example, determination section 208determines that control information for which CRC=OK (no error) iscontrol information addressed to that mobile station by performingdemasking using that mobile station's ID number. Then determinationsection 208 outputs control information addressed to that mobilestation—that is, a resource allocation result of downlink data for thatmobile station—to extraction section 205. Determination section 208 alsodetermines a PUCCH number to be used for transmission of an ACK/NACKsignal from that mobile station from a CCE number corresponding to asubcarrier to which control information addressed to that mobile stationhas been mapped, and outputs the determination result (PUCCH number) tocontrol section 209. For example, since control information is mapped ona subcarrier corresponding to CCE #1, determination section 208 ofmobile station 200 to which above L1/L2CCH #1 has been allocateddetermines PUCCH #1 corresponding to CCE #1 to be a PUCCH for use bythat mobile station. Similarly, since control information is mapped onsubcarriers corresponding to CCE #8 through CCE #11, determinationsection 208 of mobile station 200 to which above L1/L2CCH #6 has beenallocated determines PUCCH #8 corresponding to CCE #8 having the lowestnumber among CCE #8 through CCE #11 to be a PUCCH for use by that mobilestation.

Control section 209 controls a cyclic shift value of a ZC sequence usedfor first spreading by spreading section 214 and spreading section 219,and a Walsh sequence used for second spreading by spreading section 216,in accordance with a PUCCH number received as input from determinationsection 208. That is to say, control section 209 sets a ZC sequence witha cyclic shift value corresponding to a PUCCH number received as inputfrom determination section 208 in spreading section 214 and spreadingsection 219, and sets a Walsh sequence corresponding to a PUCCH numberreceived as input from determination section 208 in spreading section216. Also, control section 209 controls transmission signal selectionsection 222 such that, if directed to transmit a CQI in advance by basestation 100, transmission signal selection section 222 selects CQIsignal transmission, or if not directed to transmit a CQI, transmissionsignal selection section 222 transmits an ACK/NACK signal generatedbased on CRC=NG (error present) in determination section 208.

Modulation section 213 modulates an ACK/NACK signal received as inputfrom CRC section 212, and outputs this modulated signal to spreadingsection 214. Spreading section 214 performs first spreading of theACK/NACK signal by a ZC sequence set by control section 209, and outputsan ACK/NACK signal after first spreading to IFFT section 215. IFFTsection 215 performs IFFT processing on the ACK/NACK signal after firstspreading, and outputs an ACK/NACK signal after IFFT to spreadingsection 216. Spreading section 216 performs second spreading of theACK/NACK signal with a CP by a Walsh sequence set by control section209, and outputs an ACK/NACK signal after second spreading to CP addingsection 217. CP adding section 217 adds the same signal as at the end ofthe ACK/NACK signal after IFFT to the front of that ACK/NACK signal as aCP, and outputs the resulting signal to transmission signal selectionsection 222. Modulation section 213, spreading section 214, IFFT section215, spreading section 216, and CP adding section 217 function as anACK/NACK signal transmission processing section.

Modulation section 218 modulates a CQI signal and outputs the modulatedsignal to spreading section 219. Spreading section 219 spreads the CQIsignal by a ZC sequence set by control section 209, and outputs a CQIsignal after spreading to IFFT section 220. IFFT section 220 performsIFFT processing on the CQI signal after spreading, and outputs a CQIsignal after IFFT to CP adding section 221. CP adding section 221 addsthe same signal as at the end of the CQI signal after IFFT to the frontof that CQI signal as a CP, and outputs a CQI signal to which a CP hasbeen added to transmission signal selection section 222.

Transmission signal selection section 222 selects either an ACK/NACKsignal received as input from CP adding section 217 or a CQI signalreceived as input from CP adding section 221 according to the setting ofcontrol section 209, and outputs the selected signal to radiotransmission section 223 as a transmission signal.

Radio transmission section 223 performs transmission processing such asD/A conversion, amplification, and up-conversion on the transmissionsignal received as input from transmission signal selection section 222,and transmits the signal to base station 100 (FIG. 8) from antenna 201.

Next, a detailed description will be given of CCEs corresponding toPUCCHs of mobile stations that are referenced in control channelallocation by control channel allocation section 102 (FIG. 8).

FIG. 10 is a drawing showing CCEs corresponding to PUCCHs used by mobilestations. Here too, as in the above description, it is assumed that aCCE number and a PUCCH number defined by a ZC sequence cyclic shiftvalue and Walsh sequence number are mapped on a one-to-one basis. Thatis to say, it is assumed that CCE #1 and PUCCH #1, CCE #2 and PUCCH #2,CCE #3 and PUCCH #3, and so on, are mutually mapped.

In FIG. 10, CCEs corresponding to PUCCHs for mobile station use areshown divided into CCEs used for ACK/NACK from a mobile station, CCEsused for a CQI from a mobile station, and unusable CCEs. A CCE forACK/NACK use is a CCE corresponding to a PUCCH used for ACK/NACKtransmission from a mobile station, while a CCE for CQI use is a CCEcorresponding to a PUCCH used for CQI transmission from a mobilestation. An unusable CCE is a CCE corresponding to a PUCCH that cannotbe employed as a PUCCH for mobile station use.

In FIG. 10, CCEs #1, #2, #4, #5, #6, #7, #9, . . . , #14, #15, #17, and#18 are for ACK/NACK use, and the cyclic shift interval of these CCEs isset to 2, a level at which inter-code interference does not occur. CCE#8 is for CQI use, and CCEs #3 and #15 are unusable CCEs. The reason formaking CCE #8 for CQI use and making CCEs #3 and #15 unusable is tomaintain the cyclic shift interval between ZC sequences at a level oftwo or above at which inter-code interference does not occur. That is tosay, by maintaining a cyclic shift interval of two or more between a CCEfor CQI use and the nearest CCE for ACK/NACK use (here, CCE #9)following a CCE for CQI use in the time domain (the direction of thearrow indicating the horizontal axis in FIG. 10), inter-codeinterference between a CQI signal and ACK/NACK can be suppressed. Here,the ZC sequence cyclic shift interval between CCE #8 and CCEs #2 and #14is 1—that is, less than 2. However, since inter-code interference iscaused by a delayed wave, it is not necessary to consider the effect ofinterference by CCE #8 upon CCEs #2 and #14 located before CCE #8 in thetime domain. Conversely, for the same reason—that is, the fact thatinter-code interference is caused by a delayed wave—the effect ofinterference by CCE #2 and #14 upon CCE #8 cannot be ignored. However,since an ACK/NACK signal has greater influence on throughput than a CQIsignal, provision has here been made for greater emphasis to be placedon ACK/NACK signal transmission quality than on CQI signal transmissionquality. That is to say, a cyclic shift interval between a CCE for CQIuse and a CCE for ACK/NACK use located after the CCE for CQI use is madelarger than a cyclic shift interval between a CCE for CQI use and a CCEfor ACK/NACK use located before the CCE for CQI use.

When CCEs corresponding to PUCCHs for ACK/NACK use or for CQI use suchas shown in FIG. 10 are decided, control channel allocation section 102forms an L1/L2CCH that makes these CCEs a minimum number in accordancewith the number necessary for carrying control information.

Thus, according to this embodiment, a base station performs controlchannel allocation so as to maintain a ZC sequence cyclic shift intervalof a PUCCH for CQI transmission with respect to a PUCCH for ACK/NACKtransmission from a mobile station at a determined value or above,enabling inter-code interference between an ACK/NACK signal and a CQIsignal that are code-multiplexed to be suppressed.

In this embodiment, a case in which CCE #8 corresponding to one cyclicshift value of 3 is employed for CQI use has been described as anexample, but the present disclosure is not limited to this, and CCEscorresponding to two or more cyclic shift values may also be employedfor CQI use. For example, CCE #8 and CCE #10 corresponding to two cyclicshift values of 3 and 7 may be employed for CQI use as shown in FIG. 11.Here too, provision is made for the interval of CCE #8 and CCE #10 forCQI use with respect to following CCEs #9 and #11 for ACK/NACK use to bemaintained at two or more.

Furthermore, a cyclic shift value with respect to a CCE for CQI use maybe made common to all cells.

Embodiment 2

A base station and mobile station according to Embodiment 2 have thesame kind of configurations as a base station (see base station 100 inFIG. 8) and mobile station (see mobile station 200 in FIG. 9) accordingto Embodiment 1, and differ in regard to part of the processingperformed by the control channel allocation section (control channelallocation section 102 shown in FIG. 8).

FIG. 12 is a drawing showing CCEs corresponding to PUCCHs used by mobilestations, which are referenced by a control channel allocation sectionaccording to this embodiment. FIG. 12 is basically similar to FIG. 10,and therefore points of difference will be described here.

As shown in FIG. 12, a base station according to this embodiment employsadjacent CCEs #3 and #15 following a cyclic shift value including asmaller number of CCEs for ACK/NACK use among cyclic shift valuesincluding CCEs for ACK/NACK use as CCEs for CQI use. By this means, thenumber of CCEs for ACK/NACK use (here, CCE #8) with respect to CCEs #3and #15 for CQI use becomes one, and interference of a CCE for ACK/NACKuse with respect to CCEs for CQI use may be suppressed.

Thus, according to this embodiment, a base station performs controlchannel allocation so that an adjacent PUCCH becomes for CQI use after acyclic shift value including a smaller number of PUCCHs for ACK/NACKuse, while maintaining a ZC sequence cyclic shift interval of a PUCCHfor CQI transmission with respect to a PUCCH for ACK/NACK transmissionfrom a mobile station at a predetermined value or above, enablinginter-code interference between an ACK/NACK signal and a CQI signal thatare code-multiplexed to be further suppressed.

In this embodiment, a case in which three CCEs are made CCEs that arefor CQI use or unusable has been described as an example, but thepresent disclosure is not limited to this, and four CCEs may also bemade CCEs for CQI use or unusable CCEs, as shown in FIG. 13.Furthermore, five or more CCEs may also be made CCEs for CQI use orunusable CCEs.

Embodiment 3

In Embodiment 3, control channel allocation will be described for a casein which a cyclic shift interval between PUCCHs used by mobile stationsis 3 or more.

A base station and mobile station according to Embodiment 3 have thesame kind of configurations as a base station (see base station 100 inFIG. 8) and mobile station (see mobile station 200 in FIG. 9) accordingto Embodiment 1, and differ in regard to part of the processingperformed by the control channel allocation section (control channelallocation section 102 shown in FIG. 8).

FIG. 14 is a drawing showing CCEs corresponding to PUCCHs used by mobilestations, which are referenced by a control channel allocation sectionaccording to this embodiment. FIG. 14 is basically similar to FIG. 10,and therefore points of difference will be described here.

As shown in FIG. 14, a base station according to this embodiment employsCCEs #2 and #10 as CCEs for CQI use, and makes CCE #6 an unusable CCE,so that a cyclic shift interval between a CCE for ACK/NACK use and a CCEfor CQI use becomes 3 or more.

The kind of CCE arrangement method shown in FIG. 14 is obtained asfollows. Namely, if it is wished to employ some CCEs for ACK/NACK usesuch as shown in FIG. 15 as CCEs for CQI use, one possibility is toemploy CCE #2 as a CCE for CQI use and to make CCEs #6 and #10 unusableCCEs as shown in FIG. 16, so that a cyclic shift interval between a CCEfor ACK/NACK use and a CCE for CQI use becomes 3 or more. Now, if the ZCsequence cyclic shift value of CCEs #9 through #12 in FIG. 16 is reducedby 2 to suppress interference of CCE #9 for ACK/NACK use for CCE #2 forCQI use, FIG. 14 is obtained.

Thus, according to this embodiment, a base station can suppressinter-code interference between an ACK/NACK signal and a CQI signal thatare code-multiplexed even if CCEs with a cyclic shift interval of threeor more are allocated to a mobile station.

In this embodiment, a case in which the Walsh length is 3 has beendescribed as an example, but the present disclosure is not limited tothis, and can also be applied to a case in which the Walsh length isfour or more. FIG. 17 is a drawing showing CCEs corresponding to PUCCHsused by mobile stations when the Walsh length is four, and four Walshcodes are used. In FIG. 17, CCEs #2 and #10 are employed as CCEs for CQIuse and CCEs #6 and #14 are made unusable CCEs, so that a cyclic shiftinterval between a CCE for ACK/NACK use and a CCE for CQI use becomes 3or more.

This concludes a description of example embodiments.

A radio communication apparatus and response signal spreading methodaccording to the present disclosure are not limited to theabove-described embodiments, and various variations and modificationsmay be possible without departing from the scope of the presentdisclosure. For example, it is possible for embodiments to beimplemented by being combined appropriately. For instance, a Walshsequence with a sequence length of four or more may also be used inEmbodiment 1 and Embodiment 2.

In the above embodiments, ACK/NACK signals and CQIs have been describedas a plurality of response signals from a plurality of mobile stationsas an example, but the present disclosure is not limited to this, andthe present disclosure may also be applied to a case in which two kindsof response signals of different importance from a plurality of mobilestations, other than ACK/NACK signals and CQI signals—for examplescheduling request signals and ACK/NACK signals—are code-multiplexed.

A mobile station may also be referred to as a UE, a base stationapparatus as Node B, and a subcarrier as a tone. A CP may also bereferred to as a guard interval (GI).

The error detection method is not limited to CRC.

Methods of performing transformation between the frequency domain andthe time domain are not limited to IFFT and FFT.

In the above embodiments, cases have been described in which the presentdisclosure is applied to a mobile station. However, the presentdisclosure can also be applied to a fixed solid-state radiocommunication terminal apparatus, or a radio communication relay stationapparatus that performs operations equivalent to a mobile stationvis-a-vis a base station. That is to say, the present disclosure can beapplied to all radio communication apparatuses.

In the above embodiments, cases have been described by way of example inwhich embodiments are configured as hardware, but it is also possiblefor embodiments to be implemented by software.

Each function block employed in the description of each of theaforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC”, “system LSI”, “super LSI”, or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells within an LSI can be reconfigured is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2007-211102, filed onAug. 13, 2007, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present disclosure is suitable for use in a mobile communicationsystem or the like.

1. A base station apparatus, comprising: a transmitter configured totransmit, to a plurality of mobile stations, control information on acontrol channel element (CCE), wherein the CCE is associated with aphysical uplink control channel (PUCCH) and the PUCCH is determinativeof a cyclic shift value among a plurality of cyclic shift valuescomprising a set of channel quality indicator (CQI) cyclic shift valuesand a set of acknowledgement/negative acknowledgement (ACK/NACK) cyclicshift values, with one or more unused cyclic shift values separating thesets of CQI cyclic shift values and ACK/NACK cyclic shift values; and areceiver configured to receive: CQI signals transmitted by one or moremobile stations of the plurality using respective CQI cyclic shiftvalues of the set of CQI cyclic shift values; and ACK/NACK signalstransmitted by one or more mobile stations of the plurality usingrespective ACK/NACK cyclic shift values of the set of ACK/NACK cyclicshift values.
 2. The base station of claim 1 wherein an unused cyclicshift value is positioned after a CQI cyclic shift value and before anACK/NACK cyclic shift value.
 3. The base station of claim 1 wherein anunused cyclic shift value is positioned after an ACK/NACK cyclic shiftvalue and before a CQI cyclic shift value.
 4. The base station of claim1 wherein an unused cyclic shift value is positioned before the set ofCQI cyclic shift values and a second unused cyclic shift value ispositioned after the set of CQI cyclic shift values.
 5. The base stationof claim 1 wherein an unused cyclic shift value is positioned after anACK/NACK cyclic shift value and a second unused cyclic shift value ispositioned before a second ACK/NACK cyclic shift value.
 6. The basestation of claim 1 wherein an unused cyclic shift value is positionedafter an ACK/NACK cyclic shift value and a second unused cyclic shiftvalue is positioned before a second ACK/NACK cyclic shift value, and aCQI cyclic shift value is positioned between the unused cyclic shiftvalue and the second unused cyclic shift value.
 7. The base station ofclaim 1 wherein an unused cyclic shift value is positioned before theset of CQI cyclic shift values and after an ACK/NACK cyclic shift value,and a second unused cyclic shift value is positioned before a secondACK/NACK cyclic shift value and after the set of CQI cyclic shiftvalues.
 8. The base station of claim 1 wherein the set of CQI cyclicshift values consists of a single cyclic shift value.
 9. The basestation of claim 1 wherein the unused cyclic shift values consists of asingle cyclic shift value.
 10. The base station of claim 1 wherein anunused cyclic shift value is cyclically subsequent to a CQI cyclic shiftvalue.
 11. The base station of claim 1 wherein an unused cyclic shiftvalue is cyclically subsequent to an ACK/NACK cyclic shift value. 12.The base station of claim 1 wherein an unused cyclic shift value iscyclically subsequent to an ACK/NACK cyclic shift value, and a secondunused cyclic shift value is cyclically subsequent to a CQI cyclic shiftvalue.
 13. The base station of claim 1 wherein an unused cyclic shiftvalue is cyclically subsequent to an ACK/NACK cyclic shift value, and asecond unused cyclic shift value is cyclically subsequent to a CQIcyclic shift value, and the CQI cyclic shift values is positionedbetween the unused cyclic shift value and the second unused cyclic shiftvalue.
 14. The base station of claim 1 wherein an unused cyclic shiftvalue is incrementally shifted from a CQI cyclic shift value by a unitof cyclic shift value and decrementally shifted from an ACK/NACK cyclicshift value by the unit.
 15. The base station of claim 1 wherein anunused cyclic shift value is incrementally shifted from an ACK/NACKcyclic shift value by a unit of cyclic shift value and decrementallyshifted from a CQI cyclic shift value by the unit.
 16. The base stationof claim 1 wherein an unused cyclic shift value is incrementally shiftedfrom an ACK/NACK cyclic shift value by a unit of cyclic shift value andan second unused cyclic shift value is decrementally shifted from ansecond ACK/NACK cyclic shift value by the unit.
 17. The base station ofclaim 1 wherein an unused cyclic shift value is incrementally shiftedfrom an ACK/NACK cyclic shift value by a unit of cyclic shift value anddecrementally shifted from a CQI cyclic shift value by the unit, and ansecond unused cyclic shift value is decrementally shifted from an secondACK/NACK cyclic shift value by the unit and decrementally shifted from aCQI cyclic shift value by the unit.
 18. The base station apparatus ofclaim 1 wherein the receiver receives an ACK/NACK signal transmittedfrom a first mobile station of the plurality of mobile stations and aCQI signal transmitted from another mobile station of the plurality,which are mapped to a same symbol.
 19. The base station apparatus ofclaim 1 wherein the receiver receives an ACK/NACK signal transmittedfrom one of the mobile stations of the plurality, which iscode-multiplexed with a CQI signal transmitted from another mobilestation of the plurality, or the receiver receives a CQI signaltransmitted from one of the mobile stations of the plurality, which iscode-multiplexed with an ACK/NACK signal transmitted from another mobilestation of the plurality.
 20. The base station apparatus of claim 1wherein the receiver receives a CQI signal spread with a sequencedefined by one of the set of CQI cyclic shift values, and an ACK/NACKsignal spread with a sequence defined by one of the set of ACK/NACKcyclic shift values.
 21. The base station apparatus of claim 1 whereinthe receiver receives the CQI signal transmitted on a PUCCH, an index ofwhich is specified from the control information, and the ACK/NACK signaltransmitted on a PUCCH, an index of which is specified from the controlinformation.
 22. The base station of claim 1 wherein the set of CQIcyclic shift values, the set of ACK/NACK cyclic shift values, and theone or more unused cyclic shift values are mutually exclusive for eachsymbol.
 23. The base station of claim 1 wherein the control informationincludes mobile station identification information indicating a mobilestation of the plurality to which the control information is addressed.24. A method, comprising: transmitting, to each of a plurality of mobilestations, control information on a control channel element, wherein theCCE is associated with a physical uplink control channel (PUCCH) and thePUCCH is determinative of a cyclic shift value among a plurality ofcyclic shift values, the plurality of cyclic shift values comprising aset of channel quality indicator (CQI) cyclic shift values and a set ofacknowledgement/negative acknowledgement (ACK/NACK) cyclic shift values,with one or more unused cyclic shift values separating the sets of CQIcyclic shift values and ACK/NACK cyclic shift values; receiving CQIsignals transmitted by one or more mobile stations of the pluralityusing respective CQI cyclic shift values of the set of CQI cyclic shiftvalues; and receiving ACK/NACK signals transmitted by one or more mobilestations of the plurality using respective ACK/NACK cyclic shift valuesof the set of ACK/NACK cyclic shift values.
 25. The method of claim 24wherein the set of CQI cyclic shift values, the set of ACK/NACK cyclicshift values, and the one or more unused cyclic shift values aremutually exclusive for each symbol.
 26. The method of claim 24 whereinan unused cyclic shift value is positioned before the set of CQI cyclicshift values and a second unused cyclic shift value is positioned afterthe set of CQI cyclic shift values.
 27. The method of claim 24 whereinan unused cyclic shift value is positioned before the set of ACK/NACKcyclic shift values and a second unused cyclic shift value is positionedafter the set of ACK/NACK cyclic shift values.
 28. A non-transitorycomputer-readable memory medium whose contents cause a base station toperform a method, the method comprising: transmitting, to a plurality ofmobile stations, control information on a control channel element,wherein the CCE is associated with a physical uplink control channel(PUCCH) and the PUCCH is determinative of a cyclic shift value among aplurality of cyclic shift values, the plurality of cyclic shift valuescomprising a set of channel quality indicator (CQI) cyclic shift valuesand a set of acknowledgement/negative acknowledgement (ACK/NACK) cyclicshift values, with one or more unused cyclic shift values separating thesets of CQI cyclic shift values and ACK/NACK cyclic shift values;receiving CQI signals transmitted by one or more mobile stations of theplurality using respective CQI cyclic shift values of the set of CQIcyclic shift values; and receiving ACK/NACK signals transmitted by oneor more mobile stations of the plurality using respective ACK/NACKcyclic shift values of the set of ACK/NACK cyclic shift values.
 29. Thenon-transitory computer-readable memory medium of claim 28 wherein anunused cyclic shift value is positioned before the set of CQI cyclicshift values and a second unused cyclic shift value is positioned afterthe set of CQI cyclic shift values.
 30. The non-transitorycomputer-readable memory medium of claim 28 wherein the set of CQIcyclic shift values, the set of ACK/NACK cyclic shift values, and theone or more unused cyclic shift values are mutually exclusive for eachsymbol.
 31. The non-transitory computer-readable memory medium of claim28 wherein a received CQI signal is spread by one of the mobile stationsof the plurality with a sequence defined by one of the set of CQI cyclicshift values, and a received ACK/NACK signal is spread by one of themobile stations of the plurality with a sequence defined by one of theset of ACK/NACK cyclic shift values.